Guide wires are generally known in the art. They are, for example, used in connection with the treatment of coronary diseases, where an x-ray of a blood vessel may be done to detect the presence of an occlusion, which, however, does not show the cross section of a stenosis. It is accepted that the best way to diagnose the significance of the stenosis is to perform a measurement of the blood pressure upstream and downstream of the stenosis. In this case, a guide wire is used to position a pressure-measuring sensor in the area of interest. Once the guide wire is positioned, a catheter is slid over the guide wire and a balloon dilation may then be done. The electrical signals from the pressure-measuring sensor at the distal end of the guide wire are lead through conductors embedded in the guide wire to a male connector at the proximal end of the guide wire. In use, the male connector is connected to a female connector and the signals from the pressure-measuring sensor are transferred to an interface, which converts the signals and presents them in the desired form for an operator.
The male connector disposed at the proximal end of the guide wire comprises basically a core wire, a plurality of conductors, a plurality of conductive members, and insulating material therebetween. When the male connector is connected to the female connector, the conductive members transfer the electrical signals from the conductors of the male connector to similar conductive members inside the female connector. The core wire, which conventionally extends through the guide wire, is used to prevent kinks, to provide strength to the guide wire and to hold the guide wire together. Especially when the male connector is inserted into the female connector, there exists a substantial risk of over-bending the male connector or damaging the thin conductors inside the male connector. The core wire inside the male connector is therefore normally made of a material with high modulus of elasticity, such as stainless steel. Examples of such male connectors are disclosed in U.S. Pat. Nos. 5,178,159 and 5,938,624.
From the above, it should be obvious that the core wire should be as large as possible, so that a large amount of high strength material is provided inside the male connector, while leaving enough room for the conductors and insulation to fit within the guide wire. In U.S. Pat. Nos. 5,178,159 and 5,938,624 it is assumed that the core wire is cylindrical and that the conductors are disposed at the outside of the core wire. With this shape of the core wire, the total configuration consisting of the core wire and the conductors will occupy a large part of the space inside the male connector, without the core wire and the thin conductors themselves actually utilizing an optimum of the available space, or, with other words, there is an excess of insulating material inside the male connector. Here it should be mentioned that the available space inside the guide wire is limited by the diameter of the catheter that is slid over the guide wire. Since the catheter also is slid over the male connector, which extends from the proximal end of the guide wire, the size of the entire male connector is also limited by the diameter of this catheter. The nominal diameter of a conventional small catheter may be as small as 0.355 mm, which provides an upper limit for the diameter of a male connector used together with such a catheter.
As mentioned above, the core wire conventionally extends through the guide wire, all the way from the sensor at the distal end of the guide wire to the male connector at the proximal end of the guide wire, where the core wire provides stiffness to the male connector. For such a long core wire, the most economical and practical shape of the core wire is cylindrical, and the conventional thinking has been to keep the cylindrical shape of the core wire also inside the male connector, despite the disadvantage that the total configuration consisting of the core wire and the conductors occupies less than the optimum of the available space, which involves the risk that the male connector will be bent or damaged when inserted into the female connector.
Consequently, there exists a need for a male connector having a core wire with such a shape that the total configuration consisting of the core wire, conductors and insulating material makes an optimal use of the available space inside the male connector. In order to keep the cylindrical shape of the part of the core wire that extends from the male connector to the sensor, the male connector should preferably constitute a separate unit, which can be mounted at the proximal end of an existing guide wire. Obviously, the last requirement implies that the core wire inside the male connector is different from the core wire inside the rest of the guide wire.